Wally had a secret thought
That he just had to tell.
Wendy sat four desks away -
He did not want to yell.
How did our Wally do it
So no one else could see?
To send a secret message,
Some candle wax is key!

Please note:  All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.

Kids, Wally and Wendy needed these few essential items to send secret messages: a sheet of white paper, a white candle, watercolor paint and paintbrush, and water. Make up a short secret message and write it on the paper with your candle. It will be hard to see but try your best. Paint over the entire paper with the watercolors. Now can you read the writing more easily? Why did Wally and Wendy choose wax to write their messages? All waxes contain fats or oils. Waxes are made from petroleum oil, animal fats, or plant oils. Watercolor paint has water in it. As you know, oil and water don't mix. Water molecules and oil molecules are simply not attracted to each other, and so the paint will just slide off the wax. The paint sticks to the paper because it is attracted to the paper fibers.

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Kathleen Carrado Gregar, PhD, Argonne National Labs 
[email protected]
March 1998

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Taken From: Apples, Bubbles, and Crystals: Your Science ABCs, by A. Bennett & J. Kessler, 1996, McGraw Hill, NY.